Do I need PPP base data (or precise point) before conducting a survey?

Hello,

I was wondering if I can proceed with a survey while receiving an RTK fixed solution without first establishing PPP data for the base (a precise base location)? Or if I can survey a site while the base is collecting PPP data and then apply a correction factor later.

For example, if I was to set up over a point and input the location for the base based on single solution coordinates from the rover at the point of interest and then later get the exact location of the base via NRCAN PPP data would I be able to apply a correction factor to all my points?

You can do both, depending on your needs for immediate global accuracy.

Yep, easy to do. Can be done in QGIS etc, and even just in Excel.

3 Likes

Hi Jacob,

Cannot but agree with Christian! Just wanted to add some details.

When you average the base’s position with a Single solution, you obtain only relative accuracy. It means the rover’s coordinates are accurate to the base. It is enough for some applications such as volumetric measurements.

To achieve absolute accuracy after the survey, you can upload the base’s log to a PPP service, calculate the difference between the averaged and PPP base positions, and apply it to all the points.

If you’d like to learn more about absolute and relative accuracy, check the corresponding section in our Placing the base guide.

Awesome, thanks for the response. I have a few follow up questions.

My first question is, in your opinion what would be the best way to conduct a survey assuming that I will be using PPP data later to get an accurate base position?
Would it be best to set up the base over a known point with base mode set to average single (for coordinate method), conduct the survey, then download the data required for PPP before taking down the set up, and then finally manually enter the corrections in an excel sheet when I receive the accurate coordinates?

My second question is, is the correction factor as simple as taking the difference between the single solution base location and the base location I would get from the PPP data and then applying that difference to each point (obviously accounting for the direction of the shifts)?

My last question is how long should I average a single position in base mode if I plan on making corrections later? It seems to me like it wouldn’t matter how short the averaging time is because I will be accounting for the change later anyway.

Thanks again,

Jacob

Hi Jacob,

You absolutely got the workflow. I’d set up the base, average its position in Single, start logs recording and survey points at the same time. And after that, would just apply the shift in Excel.

Yep, just take the difference and add it to the points.

It’s 2 minutes, by default. And it should work fine for your case too. The precision of a Single solution is a few meters anyway. So, the averaging time doesn’t matter.